1. Field of the Invention
The present invention relates to diaphragm blades used for optical apparatuses such as film cameras, video cameras, and digital cameras, a method of manufacturing the diaphragm blades, and a light quantity controller having the diaphragm blades.
2. Description of the Related Art
Cameras, such as video cameras and digital cameras, having solid-state image pickup elements and cameras using films usually have diaphragm devices (light quantity controllers) that control an aperture diameter to check a depth of focus of a lens, and to control the light quantity of an object focused on a film or a solid-state image pickup element. Also, optical apparatuses that project images may have light quantity controllers. Such light quantity controllers typically include a type in which a plurality of light-shielding blades (diaphragm blades) are used to change an aperture diameter around an optical axis like an iris, and a type in which two diaphragm blades are relatively moved in opposite directions to change an aperture diameter.
The former type can continuously change the aperture diameter, and hence, a desired aperture diameter can be obtained. However, to obtain an aperture approximate to a circle, it is necessary to increase the number of diaphragm blades, thereby increasing the cost.
On the other hand, the latter type uses a small number of diaphragm blades, and thus can save costs. However, it is difficult to obtain an aperture approximate to a circle.
The diaphragm blades usually have light-shielding blade bases and shaft portions for rotation of the blade bases.
To form a shaft at a blade, hitherto, a metal shaft is arranged at a sheet metal or a plastic sheet by mechanical caulking, or resin is provided at a blade sheet by outset molding. These methods require a large number of man hours, and have problems in reliability. In addition, a caulking mark of the shaft, or a blade attaching portion at the shaft due to the outset molding may protrude from the back side of the blade with the shaft, and the caulking mark or blade attaching portion may be hooked to a plate when the blade is driven.
In light of this, as shown in FIG. 14A, Japanese Patent Laid-Open No. 6-317826 suggests a diaphragm blade 60 having a blade substrate 61 made of synthetic resin, and protruding engagement portions 62 and 63, the blade substrate 61 being integrally formed with the protruding engagement portions 62 and 63 by injection molding. Hence, the number of man hours for manufacturing the diaphragm blades, and the manufacturing cost can be markedly reduced.
Also, as shown in FIG. 14B, Japanese Patent Publication No. 6-68595 suggests an exposure control blade 70 manufactured such that a notch is formed at a dowel-holding position of a blade, a blade is conveyed to a die of injection molding for molding a dowel at the blade, the notch is pushed upward by a part of the die to protrude into a cavity of the die during clamping of the blade, and the notch is covered with and held by resin of the dowel when the dowel is injection-molded. Hence, the resin can cover and hold the dowel at the notch without making a hole in the diaphragm blade, or in a shutter blade, thereby increasing a dowel-holding strength.
However, with the above-described diaphragm blade, the thickness of the shaft portion is larger than the thickness of the blade base, and thus, flowability of the resin during the injection molding may be small, or the shaft portion may be deformed. This may deteriorate dimensional accuracy of the shaft portion. The problem becomes more noticeable as the thickness of the blade base is reduced. In contrast, if the thickness of the blade base is increased, a load during drive of the blade may become large. The blade driver such as a motor has to be increased in size accordingly, and as a result, the entire apparatus may become large.